Indexed on: 11 Jul '17Published on: 27 Jun '17Published in: Physics Letters B
We present the QCD predictions for the azimuthal cos2φcos2φ asymmetry in charm leptoproduction for the kinematics of the COMPASS experiment at CERN. The asymmetry is predicted to be large, about 15%. The radiative corrections to the QCD predictions for the cos2φcos2φ distribution are estimated to be small, less than 10%. Our calculations show that the azimuthal asymmetry in charm production is well defined in pQCD: it is stable both perturbatively and parametrically, and practically insensitive to theoretical uncertainties in the input parameters. We analyze the nonperturbative contributions to the cos2φcos2φ distribution due to the gluon transverse motion in the target and the c-quark fragmentation. Because of the c-quark low mass, the nonperturbative contributions are expected to be sizable, about (30–40)%. We conclude that extraction of the azimuthal asymmetries from available COMPASS data will provide valuable information about the transverse momentum dependent distribution of the gluon in the proton and the c -quark hadronization mechanism. Finally, we discuss the cos2φcos2φ asymmetry as a probe of the gluonic analogue of the Boer–Mulders function, <img height="22" border="0" style="vertical-align:bottom" width="22" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0370269317305336-si3.gif">h1⊥g, describing the linear polarization of gluons inside unpolarized proton.